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    <title>dev::Web3</title>
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  <body>
    <div class="box">
      best block #<span id="blockNumber">unknown</span>
    </div>
    <script>
      window.setInterval(function () {
        window.web3.eth.getBlockNumber(function (error, blockNumber) {
          if (error) {
            console.error('error', error);
            return;
          }

          document.getElementById('blockNumber').innerHTML = blockNumber;
        });
      }, 1000);
    </script>
  </body>
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